Clashes erupted in one of three Tunisian cities where tens of thousands of people demonstrated over their declining economic situation, calling for greater investment in their impoverished regions.

Protesters on Wednesday set fire to the office of Tunisia's ruling Islamist party in the southern mining town of Gafsa, as strikes were observed in areas amid rising discontent and political deadlock.

Hundreds of demonstrators attacked the Ennahda party's headquarters in the poor central region and tried to break into the governor's office before being dispersed by police firing tear gas.

Protesters chanted slogans calling for the fall of the regime.

General strikes were called in the northwestern city of Siliana, Gafsa and in Gabes, which is along the southeastern coast, calling for greater government investment.

In Siliana, the strike was called to commemorate the police repression of anti-government protests a year ago in which about 300 people were injured.

Hundreds gathered on Wednesday outside the governor's office to remember the victims, hurling rocks at the police, who threw rocks back at them and then drove into the crowd of protesters to try and disperse them.

"We live in desperate conditions because of unemployment, poverty and misery and we are only asking to live in dignity," said Badreddine Hamlaoui, a 19-year-old who lost an eye during protests in Siliana last year. "I ask myself why Siliana is neglected and excluded from development."

In Gabes, most public offices and businesses were closed in response to the UGTT's call to strike, and a large protest was held in the early afternoon, with no incidents reported.

Under an ambitious roadmap brokered by mediators last month, the Islamist party Ennahda and opposition pledged to negotiate an interim government of independents. But the talks were suspended shortly afterwards with the two sides unable to agree a future prime minister.

According to the National Institute of Statistics, unemployment is already a high 15.7 percent in the country, but in places like Siliana or Sidi Bouzid it rises to 20-29 percent, double that for young people.